On a low hill in County Kildare, amid ordinary pasture land, sits a circular earthwork that has quietly resisted easy classification. Roughly fifteen metres across, it is ringed by a low bank and, crucially, by an external fosse, which is the term for the shallow ditch that runs around the outside of many prehistoric and early medieval earthworks. That fosse is what sets it apart from its immediate neighbours.

The site sits alongside several ringbarrows, the low, circular burial mounds that dot the Irish landscape and typically date from the Bronze Age. In size and shape, this enclosure is close enough to those mounds that it might easily be mistaken for one. But where a ringbarrow's defining feature is its raised platform, built up to cover a burial, an enclosure with an external fosse points instead toward a structure designed to demarcate space, to define an inside and an outside, perhaps for habitation, ritual, or territorial purposes. The distinction sounds technical, but on the ground it changes what you are looking at entirely. Whether the Mullamast enclosure was in use at the same time as the adjacent barrows, or belongs to a different period altogether, is not something the visible earthwork can answer on its own.